What happenedJohn McCain swept primaries in Ohio, Texas, Rhode Island, and Vermont on Tuesday, piling up enough delegates to officially claim the Republican presidential nomination. McCain’s main remaining rival, former Arkansas governor Mike Huckabee, dropped out minutes after the polls closed and said he would do what he could to help elect McCain. (The New York Times, free registration)

What the commentators saidMcCain has just “completed one of the most remarkable comebacks in modern presidential politics,” said USA Today in an editorial, but he still “has a tall hill to climb” in a year that “favors Democrats.” Voters are “tired of a Republican president who took the nation into a war that won’t end and now presides over an economy that is flirting with recession. McCain is no George Bush, but Bush’s dismal approval rating”—stuck in the 30s—“is an anchor weighing down his candidacy.”

The senator from Arizona “is going to be harder for the Democrats to beat than they think," said Howard Fineman in Newsweek.com. He has overcome long odds before—as a soldier and as a politician—and he provided a glimpse of how he’ll run in his speech after securing the nomination. He said he would defend free-trade treaties, and challenged Democrats to say how they would end the Iraq war “without producing a genocidal ethnic cleansing. In short, he sounds presidential, impressively so.”

The other Republican candidates helped out McCain by “bleeding” votes from each other, said Michael Scherer in Time.com, and the Democrats are keeping his “luck” alive with the “increasingly nasty infighting” between Hillary Clinton and Barack Obama. McCain could gain strength if this “fight dampens” some of the Democrats’ enthusiasm, and Clinton’s charge that Obama is not prepared to be commander-in-chief is “exactly the message that McCain will no doubt hammer over and over again in the months to come, especially if Obama is his opponent.”